Grounding Electrode Conductor

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Smart $

Esteemed Member
Location
Ohio
Yes.

However, you can reduce the service conductor size say from meter pan to the service disconnecting means (assuming both are in close proximity), and then run a "normal-sized" GEC(s) to the disconnecting means.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Yes.

However, you can reduce the service conductor size say from meter pan to the service disconnecting means (assuming both are in close proximity), and then run a "normal-sized" GEC(s) to the disconnecting means.

Smart table 250.66 states that we must use the size of the largest service conductor. I don't see how reducing the conductors from the meter to the panel would change that.
 

Smart $

Esteemed Member
Location
Ohio
Smart table 250.66 states that we must use the size of the largest service conductor. I don't see how reducing the conductors from the meter to the panel would change that.
I agree that it goes to intent as opposed to literal interpretation.

Consider for a moment that the reduced size service conductor from meter pan to SDM is a tap (and there is a hypothetical second SDM in a separate enclosure). The GEC is based on the size of the service conductor taps supplying the SDM [250.64(D)(2)].

JMO
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Yes but you would need one grounding electrode conductor from each panel. The equivalent in most cases will be the same as the one sized for the service. I did a scenario where there could be 600-1000 kcm copper for a 400 amp service and the grounding electrode conductor would be 2/0. Two 200 amp panels would req. 2 #4. If you look at the amp of two # 4 at 75C we get 170 amps. The 2/0 gives us 175 amps.

I do see you point and I believe this may need a clarification in 2020.
 
Smart table 250.66 states that we must use the size of the largest service conductor. I don't see how reducing the conductors from the meter to the panel would change that.

That is where I was coming from. I have 750 Aluminum paralleled for a 400 amp service. Which is 2/0 copper. Didn't see how I could go less.
 

kwired

Electron manager
Location
NE Nebraska
If you run 500 aluminum from transformer to meter socket (long run) and then run 4/0 aluminum from meter socket to 200 amp service disconnecting means inside a house - and land the GEC in the service disconnecting means do you size it for the 500 or the 4/0?

I would size it for the 4/0 service entrance conductor unless someone convinces me it must be sized to the 500 underground service conductor/lateral.
 
If you run 500 aluminum from transformer to meter socket (long run) and then run 4/0 aluminum from meter socket to 200 amp service disconnecting means inside a house - and land the GEC in the service disconnecting means do you size it for the 500 or the 4/0?

I would size it for the 4/0 service entrance conductor unless someone convinces me it must be sized to the 500 underground service conductor/lateral.

I agree with you. My meter is at the road so my 750s are service entrance conductors.
 
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